Currently, the electrophotographic technology is widely applied for copying machines, laser beam printers (to be referred to as “LBPs” hereinafter), fax machines and the like because of its high-speed processability, high image quality and so on.
As an electrophotographic photosensitive body in the field of this electrophotographic technology, inorganic photoconductive substances such as selenium, selenium/tellurium alloys, selenium/arsenic alloys, cadmium sulfide and the like have mainly been used conventionally.
However, recently it is a general practice to mix an organic photoconductive substance with a binder resin to form a coating film from the viewpoint of toxicity, safety, cost, productivity and the like.
As the binder resin, various thermoplastic resins and thermosetting resins such as polymethylmethacrylate, polystyrene, vinyl polymers such as polyvinyl chloride and copolymers thereof, polycarbonate, polyester, polysulfon, phenoxy resins, epoxy resins and silicone resins have been used.
Electrophotographic photosensitive bodies using any of these various binder resins can be formed into thin films with ease by means of a cast film-forming method and hence are suitable for mass production and can be provided relatively at a low price.
Of these various resins, polycarbonate resins show relatively excellent characteristics and hence are used popularly. For this reason, uses of various polycarbonate resins have been reported.
Among them, a polycarbonate resin derived from 1,1-bis(4-hydroxyphenyl)cyclohexane as a starting monomer is used as a binder resin having excellent solubility with solvents and wear resistance as well as excellent compatibility with organic photoconductive substances (see Patent Document 1).
However, a binder resin having more excellent wear resistance is demanded recently, and a method of using a polycarbonate resin having an unsaturated double bond as a binder resin has been developed (see Patent Document 2).
The technique described in the Patent Document 2, wherein the unsaturated double bond is an allyl group as described in the examples, is to react a polycarbonate resin having the allyl groups with a cross-linking agent such as pentaerythritol-tetra(3-mercaptopropionate) and a photo polymerization initiator to form a cross link so as to improve wear resistance.
While the above technique provides means effective to improve wear resistance, the residual electric potential on the surface of the photosensitive body rises under high temperature and high humidity conditions on the assumption to be used in summer in Japan or in tropical region to produce defective images due to the influence of the cross-linking agent.
Additionally, this technique has such a disadvantage that a defective image is also produced due to the deterioration of sensitivity when a charge transport agent having an unsaturated group such as a stilbene-type agent is used, because the unsaturated group of the charge transport agent reacts with a cross-linking agent under the presence of a photo polymerization initiator or a radical initiator.
Therefore, since a photo polymerization initiator and/or a radical initiator cannot be used for the photosensitive body composition where a stilbene-type charge transport agent is used, wear resistance thereof is as low as a photosensitive body using a conventional binder resin, and hence there is room for improvements.
[Patent Document 1]
    Jpn. Pat. Appln. Laid-Open Publication No. 61-62039[Patent Document 2]    Jpn. Pat. Appln. Laid-Open Publication No. H04-291348